A stark fact: around 80% of the antibiotics by weight used in the U.S. are given not to sick human beings, but to farm animals. And for the most part, these drugs aren’t prescribed by veterinarians to save ill pigs or chickens, but instead are administered to animals in low doses in their food and water, for the purpose of growth promotion—the drugs seem to help livestock pack on weight—and prophylactially, to help them survive the packed conditions of a modern factory farm.

Now a new report by the Natural Resources Defense Council (NRDC) underscores just how lacking the FDA’s regulation of antibiotics in farm animals has been. Using FDA documents acquired through the Freedom of Information Act (FOIA), the NRDC found that the agency allowed 30 potentially harmful antibiotics—18 rated as “high risk” by the FDA itself—to remain on the market for use as additives in livestock feed and water. Despite internal FDA reviews that raised questions about the risks posed by the drugs, the additives still remain approved and many of the drugs are still on the market for food production. “The FDA knew the risks, but they still haven’t done anything to revoke the approval of these drugs,” says Avinash Kar, an attorney for the NRDC and the co-author of the new report.

The FDA has been looking at antibiotics in farm animals since 1970, when the agency convened a joint task force of experts that eventually found that the nontherapeutic use of antibiotics in livestock—meaning for growth promotion or for prophylactic use on healthy animals—could lead to resistant strains of bacteria that could threaten human health. In 1973, the FDA adopted regulations that required drug manufacturers to prove the safety of antibiotics used in animal feed and water. In 1977 the FDA found that the use penicillin and tetracyclines—two classes of antibiotics that are widely used to treat humans—in animal feed was unsafe, and proposed to withdraw approval of the drug classes. But according to NRDC’s findings, the agency never followed through.

In 2001, prompted by legislation that set aside money for the agency to look at antibiotics, FDA experts began reviewing livestock feed additives already in use that contained penicillin or tetracyclines. The additives—30 altogether—were reviewed according to two sets of criteria: the 1973 safety regulations, and 2003 guidelines meant to evaluate the safety of any new animal antibiotic drugs. (The 2003 guidelines gauged the risk of antibiotics in feed leading to resistant strains of bacteria, as well as the chance those strains can reach people and damage human health. The antibiotics would then be classified as low, medium or high risk.) The internal FDA documents unearthed by the NRDC show that agency experts found that 26 of the 30 additives had never even met the initial 1973 safety criteria. The agency also found that 18 of the 30 additives posed a “high risk” of exposing human beings to antibiotic-resistant bacteria through the food chain, according to the criteria set out by the 2003 guidelines.

For the 12 remaining additives, manufacturers hadn’t even supplied the FDA with sufficient evidence for the agency to determine the health risk they might pose to human beings. According to the NRDC, none of the 30 antibiotic feed additives in question could be approved today under the current guidelines. Because the FDA does not disclose sales of specific animal drugs, it’s impossible to know how widely those additives are still being used in animal feed. But the NRDC found evidence that at least nine of the additives are still being marketed today, and 28 of the drugs apparently still remain approved for use. The remaining two were withdrawn voluntarily from the market.

While the food industry says that restricting antibiotics in livestock would lead to sicker animals and more expensive meat, it is possible to have a major meat producing industry without the dangerous use of antibiotics for growth promotion. The European Union has banned all antibiotic growth promoters in animal feed, and Denmark—which produces about as many hogs as Iowa even though the Scandinavian country is more than three times smaller than the Hawkeye State—has banned all prophylactic uses of antibiotics in animals. But while a few food companies in the U.S. like Chipotle have touted their drug-free meat, millions of pounds of antibiotics are still being used on farms. There are a pair of bills in Congress that would curb antibiotic use in animals—the Preservation of Antibiotics for Medical Treatment Act (PAMTA) in the House and the Preventing Antibiotic Resistance Act (PARA)—but neither are likely to pass.

That leaves the FDA, which has in recent years begun to move gently on antibiotics in animal feed. Last month the agency released guidelines that ask drug manufacturers to change their labels voluntarily so that farmers would no longer be able to use the drugs for growth promotion, and instead would need a veterinarian’s prescription to use the drugs for therapeutic purposes, rather than simply allowing them to be bought over the counter. The FDA has said that voluntary guidelines will lead to faster changes in antibiotic use, largely because tougher rules could face time-consuming legal challenges from the food industry. And the agency says that once the labels on drugs have been changed, it would be illegal for the additives to be used for growth promotion—and the FDA has claimed it would take action against companies that failed to comply.

In response to the NRDC report, Siobhan DeLancey of the FDA’s Veterinary Medicine team noted that two major drug companies have expressed support for the agency’s new guidelines, which she said are informed by the FDA’s earlier scientific review of those 30 additives. She added that the FDA expects to fully implement its strategy to phase out all medically important antimicrobials—including the penicillins and tetracyclines called out by the NRDC—within three years:

The FDA is confident that its current strategy to protect the effectiveness of medically important antimicrobials, including penicillins and tetracyclines, is the most efficient and effective way to change the use of these products in animal agriculture. We note that our strategy also does not limit our authority to take future regulatory action.

But consumer and environmental groups are doubtful that much will change without a legal mandate. “The FDA has the authority to move independently on this,” says Kar. “It seems to me the FDA is using the specter of time and resources to justify a voluntary approach.” Until that changes, neither will our other drug problem.